Polydactyly, Preaxial I

Alternative Names

  • PPD1
  • Polydactyly Preaxial
  • Thumb Polydactyly
  • Thenar Hypoplasia
  • Fromont Anomaly
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Congenital malformations and deformations of the musculoskeletal system

OMIM Number

174400

Mode of Inheritance

Autosomal dominant with reduced penetrance vs. polygenic

Gene Map Locus

12q13.3

Description

Preaxial polydactyly is a congenital malformation, defined by a duplication of a digit on the radial or tibial side. Anatomically, preaxial polydactyly has been classified into different categories; Type I characterized by duplication of one or more of the skeletal components of the first digit. Thumb polydactyly itself is classified into different types, depending on the severity of the duplication. These types range from a mere splitting of the distal phalanx to a completely duplicated thumb. The most common of these types is the duplication of the proximal phalanx resting on a broad metacarpal.

Surgical treatment is the only option available. The aim of surgery is to skeletonize the extra digit and remove it at the metacarpophalangeal (MCP) joint. Post-surgery, the size of the digit is diminished. Therefore, all the soft tissue structure of the duplicated thumb is retained to make the retained thumb look bigger.

Most cases of preaxial polydactyly are sporadic and unilateral. However, several familial cases have been noted. The gene (GLI1; GLI Family Zinc Finger 1) responsible for preaxial polydactyly was mapped to the long arm of chromosome 12.

Epidemiology in the Arab World

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Other Reports

Jordan

Kenue and Abu-Hileh (1994) reported the case of a patient, born with an isolated duplication of the thumb on the left side, to consanguineous Jordanian parents, in Oman. The polydactyly was classified as preaxial polydactyly type I. X-ray analysis revealed that the thumb had a duplicated distal phalanx and a bifid proximal phalanx (Wassel Grade III). No other abnormalities, including thenar hypoplasia, were seen in the child. Hands and feet of the parents were normal. However, a study of the family history revealed that two relatives of the child's maternal grandfather, an aunt and a first cousin, had preaxial polydactyly of the feet.

[Kenue RK, Abu-Hileh MF. Familial preaxialm polydactyly type-I in an arab family. J Bah Med Soc. 2004; 6(2):91-4.]

Oman

[See Jordan > Kenue and Abu-Hileh, 1994]

Saudi Arabia

Al-Qattan et al. (2002) described an unusual case of polydactyly of the hands and feet. The ulnar 4 digits of both hands and the outer 4 digits of both feet appeared normal, and the extra digits were on the radial side of the hands and on the medial side of the feet. The pattern of polydactyly did not fit any of the well-known deformities associated with radial digital duplication such as thumb polydactyly, mirror hand, or duplicated (multiple) hands. The harmonious deformities of the hands and feet was suggestive of a genetic alteration to the development of all 4 limb buds, but the case did not fit any of the known syndromes that have high-level preaxial digital duplication of the hands and feet.

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